One of gear pairs known in the art is described, for example, in Patent Document 1. The gear pair described in Patent Document 1 includes a first gear and a second gear that are engaged and paired with each other, in which the arithmetic average roughness Ra, the maximum height Ry, the skewness Rsk and the ratio Ry/Ra of arithmetic average roughness and maximum height of the tooth surfaces of the respective gears are specified. This configuration increases the amount of oil held between the tooth surfaces to reduce the coefficient of friction between the tooth surfaces, so as to improve the seizure resistance and the abrasion resistance of the tooth surfaces and also to improve the power transmission efficiency of the gears.